Engine lubricant conditioning system



H. T. BOOTH ET AL ENGINE LUBRICANT CONDISTIONING SYSTEM Aug. 9, 1949.

5 Sheets-Sheet l Filed Oct. 18, 1943 VES, 139:53

H. T. BOOTH 'E1-Al. 2,478,521

ENGINE LUBRICANT CONDITIONING SYSTEM v Aug. 9, 1949.

Filed Oct. 18, 1943 1 ENToR HAAHIY /yXi-'FHHN Tunis ,0, Oxaprr' Awa Aug. 9, 1949. H. T. BOOTH ET Al. 2,478,521

ENGINE LUBRICANT CONDITIONING SYSTEM Filed oct. 1s, 1943 3 sheets-sheet 5 M Q y w Q Q my M Q -Q/ Q .Q. Q ,/Hv... 9, w Q Q4? 7 Z 4. ,5 4 n 4 Patented ug. 9, 1.949

2,478,521 ENGINELUBRIGAT GONDITINING SYSTEM Harryi'i. Booth,-A1lan-=C. Hoffmangiand Jamesupg Olcott, Daytoxu Ohio, assignors to UnitedwAlr: s' craft; Broductsnlnm; Dayton; h10,v a c0rpo1-a-.-, v ,f

AfpplimionL october'- is, 1943; serial? Nd: 5'0'6L716' @claimen-.(01.1237196), A

Y s 1 i Y This i invention relates -`to uidl conditioningY systems; and particularly tfmeansfo itrlL-l lingI uidviscosities-througl'if introductie finto: the fluid` of a-viscosityir'nodifying'agentt articia'llyto induce-inthe'uid-a viscesity e'p resentative of any desired fluid temperatura?` respective ofthef-actual ti-zmlo'erat'ure.4

While the invention -hasapp1icatior-toiaiiy-sysl teinin which it maybe desiredl either-'tiobtai temporarily aV lchangledl-'uid Vviscosity or to )ma-iii# tain the `ii'ui'd`I at's'o'me predeterminedi degree of" viscosity, it is disclosed asA concernedi' priniarilyi With the-'viscosity` control-i ofllubricating@oil n` for'y internal #combustion engines; Asso applie'di the invention -has-l special, -thou`gh A not limited' referti" enceto aircraft and tankl engines?, andto auto* motive machinery ingeneral:

Such'machinery, Whenfunctioning in coldL Weather is subject to troublesome operation re# sulting froni'high oil viscositiesthejlubricating oil tending, whenit-he-Hengine is inactive", to'fconf geal orf become'y toovrheavily V'viscous*to`- be" forcedL easilyv vthrough ther oil: system -v and the" engine bearings.v Thus after #thekv engine "hasv been idle' for several hours, for example overnight; 'it' is' diicult to start vand slow' to lreach operating leff'r' ciency.

Iri forder to'la'void the d'c'ultiesbroug*ht*onJ byf high oil v iscosit-ies the practicehasfbeenldei' veloped of admitting to thew` lubricating system aqua-ntity of substantially rion-con'gealable fluidv whichactsfasa diluent'; changing the physical characteristics ofi-theioil in order to4 hold the" lubricant to 'a' low viscosity irrespective of tern'-` perature. Thediluentordinarilysiaddedv t'o the'V oil fjus't before' shutting offv the .engine so tnat a diluted-l higmyyuuid lubricant ris`v` immediately: available whenv the'engine-is nextwstart'ed. As the temperature of the Yoil rises und'erforced cir-l culation through the f engine the diluent evaporates, theA ou returningto its Vnatural state. 'rife mannerl ofadmission ofthe diluent has' heretofoie beensuch'that the operatormust guess at or estimate'the rate and amount of dilution; That, isgassuming-it is desired to'ch'ange 100"%'oi1 to'V a Ymixture comprising "76 Y oil and 30% 'dilueht the-operator adjusts a control to' begin dilutionv an'dthen when he considers thatv suliicienttinie hase1apsed for a 3o%--di1ution of; meA vm1, he makes 4aA further adjustment to `discontinue, diluf tion.V

The prior art methodofoil dilutionfthus leaves, the relative proportions, of fthe-,oil andldiluent-to the discretionoftheopera-tor;Vv and ysuch+a= system has. eviden-t disadvantages-which it is a purr; Dose of this. invention-to overcome'.l On'cnotable' disadvantage, :is that i-the oil- 4can ,f-easily"be; tool greatlydilutedand-require a` long i warm-upf `of` the .eng-ine :order tov` evaporate -2 .enauglr diluent:

' 12o-make the onsuna-bie;roflmaximummennenJ Yl complete installation loi -V-anfoil rdilutitn':syste ofl the Eengine.A Y

The v present-A inventionf provides a constiiuctom and arrangementeofparts Whichfrepresentsfff having Ias its aim .orv obj ectautomaticregulation of `ther supplylof'y diluentl to thefoiLvV Arr object' vof vthe, inventionE is :torfobtain iaicon/'sil trol systemi'for useein'econnectionzwithiliquid cir1-'= cuits;` which-l system when setiy in i operati'onldniztiates': dilution or the 1iquidr;hand,wheir=a prede-L: termined stage L of dilution is reached;` automati-S cally4 shuts oiV the -supply tof: diluent f i Anotherl objectxis td incorporate' 2in ithesystemi-1 meanswincluding afvarably settable controlele-#V mentsforzl placingy the -oildilution-ioperation alter-fi natively .under the' complete'control--of-the op" ator; or under the' jintz'control of theopera'torl anda Viscosity' responsive zcontrol instrument- 1 Inf carryinghout such` objects;l afpractical= ein@ bodiment of-,the invention-'hasresultedincluding an yelectric circuiti andA avalve factuating`1-solenoidi comprised therein; for ,contrellinglrth supply@ of? diluent, separate switchesdspsed-:in saidcir'c t in s series for energizing and'll dee1e`rgiizing-v i saidf, solenoidgzmanualmeans for operating-one o'is 'd5'- switches-Yv and means responsive to" change viscosity .in said fluid :circulating'syste'miriope -f-'z ating another -ofsaidswitches'.

Fig. llis a diagrammatic illustration offthe'fi" vention installed-l as a systemfor-controlling= lutionv of the lubricating oil of -ana-ircraft engine? Fig'..2 isfa vieWiinvend-elevationoi'a viscosity"v responsive instrument comprised?infthesyste and't inc1udin`g:-a showingof `Aan'electr-ical "sw case attachedlto the instrument!a'riri`- enclosin switch'operatedf therebyy' y f Fig. .f3 is la' View of: the :viscosity responsive iin*VV strumentf iin vertical longitudinal isectionrtalen'i alongfth -1ine3-'3:of' Fig. 2

Figi; f 4 is a viewy of thek inst-rlmierit-l partly inf longitudinal `v"section, as viewedalong4T the line shows it as a system for diluting the lubricating oil of an aircraft engine and functioning to btain automatically a predetermined degree of dilution of the lubricating oil. Referring to Fig. l, reservoirs I I and I2 indicate respectively a tank holding gasoline or like fuel and a tank containing lubricating oil. Reservoir II has a discharge line I3 connected thereto through which the fuel is conducted to a carburetor I4. After vaporization in the carburetor the fuel is directed through a line I5 to the engine I6. Oil from the reservoir I2 is directed to the engine I6 through a discharge line I1, a drain fitting I8 and a line I9, which together constitute the inlet line for the oil flowing to the bearings of the engine. Both the fuel and the lubricating oil are delivered to the engine under pressure, an engine driven pump 2l in the line I3 being provided for feeding the fuel to the carburetor and an engine driven pump 22 in the line I9 serving in a similar manner to withdraw oil from the reservoir I2 and force it into the engine. The lubricating oil is returned to the reservoir I2 by means of aline 23 which may communicate at its engine side with the crankcase. A pump 24 in the line 23 directs the oil emerging from the engine back to the reservoir and cooperates with the pump 22 in maintaining continuous circulation of the oil during operation of the engine. In accordance with a conventional practice, there may be interposed in the oil circuit heat exchange apparatus for regulating the temperature of the oil, although vneither such a unit nor other auxiliaries here shown are essential to the operation of the present viscosity control. oil is accomplished by changing the physical properties of the oil through the addition thereto of a liquid of lower viscosity. As a matter of convenience the diluent contemplated to be employed is gasoline drawn directly from the fuel line I3, although if desired a diluent from an independent source may be supplied. Also, the point of introduction of the diluent into the oil circulatory system is not critical, and such inlet may be placed wherever found desirable on account of economy of use or structural expedience. It is here contemplated to introduce the diluent, which for the sake of clarity will hereafter be described as gasoline, into the oil inlet or feed line made up of conduits I1 and I9 and fitting I8. As shown, a conduit 25 communicates at one end with fuel line I3 and at its other end extends into the drain fitting I8, where, as the oil passes from conduit i1 to conduit I9 it may have mixed therewith a quantity of gasoline. Controlling the now through line 25 is a valve assembly 26, comprising la valve 21 normally occupying a position closing a passage through the assembly and hence the line 26, and a solenoid 28 adapted when energized to move the valve to a position opening the line 25. The solenoid 28 is in an electrical circuit including a line 29 connected to a source of current, as one side of a battery 3|. The other side of the battery has a line also running to the solenoid 28 but comprised of separate leads 32, 33 and `34 connected by control switches 35 and 36 arranged in series. When both switches 35 and 36 are closed a flow of current is established through the solenoid, and the valve 21 is opened to permit the entrance of gasoline into the lubricating system. When the electrical circuit is broken, as by the opening of switch 35 or 36, the solenoid operated valve 21 closes and the passage of gasoline through the conduit 25 is interrupted.

The switch 35 is arranged for manual adjust- Dilution of the lubricating ment, and preferably is located on the instrument panel of the airplane, while the switch 36 mai7 be remote from the instrument panel, being associated with a viscosity responsive instrument 31 and fully automatic in its operation. According to the primary method of operation both switches and 36 must be closed to effect opening of the valve 21, and dilution will continue until valve 35 is opened manually or valve 36 is opened automatically. By a secondary or alternative method unit 31 and switch 36 may be made ineffective, and the dilution system made subject to manual control alone. To this end the lead 33 is paralleled by a line 38 extending from the switch 35 to a point in lead 34 beyond switch 36. Switch 35 is constructed and arranged for movement to two operating positions, in one of which it establishes the current flow through lead 33 and switch 36 and in the other of which low is established through line 38 in by-passing relationship to the switch 36. l

As shown, a signal lamp 39 is interposed in a position between lines 29 and 34 in such wise that the lamp will light when the circuit is closed and be extinguished when the circuit is opened. The signal lamp, which may be mounted on the instrument panel, thus gives a visual indication when lighted that dilution is taking place.

Considering now the viscosity responsive instrument 31 and the manner in which it effects automatic control of the system it will be observed that a continuous stream of oil is delivered to the instrument through a conduit 4I which communicates at its inlet end with the oil line I9 at the pressure side of the feed pump 22. After passing through the instrument the oil is discharged to a line 42 which is here indicated as leading to the engine crankcase, but may be connected to any other low pressure area such as the reservoir I2 or the suction side of the pump 22. The function of the viscosity responsive instrument is to measure or determine the viscosity of the circulating oil and to open the switch 36 when a predetermined degree of dilution is obtained.

The present invention being directed to the system as a Whole, it is not intended that any limitation should be placed on the kind of control instru-ment to be embodied therein. For completeness of disclosure a specific form of instrument is illustrated and described herein, which instrument is the subject of a separate application Serial No. 506,717, filed by Harry T. Booth of even date herewith, for Viscosity responsive means and now Patent No. 2,400,910.

Referring to Figs. 2-5, the instrument is cornprised of a body portion 43, providing three longitudinal bores 44, 45 and 46, the body having a somewhat triangular shape with the bores 45 and 46 vertically spaced along the base thereof and the bore 44 substantially centered and offset toward the apex. The bores 45 and 46 extend through the body while the bore 44 extends only partly therethrough. That end of the body portion through which all three bores open is closed by a single plate or cap 41, while at the opposite end of the body the bores 45 and 46 are capped by separate closures 48 and 49. In substantial alignment with the bore 44 is an opening in the plate 41 which receives a gland 5I (see Fig. 4). The interior of the gland 5I is screwv threaded for coupling to the oil line 4I and its inner end has attached thereto, as by soldering, a tubular screen 52 through which the oil discharges int-o the bore 44. The bore 44 which thus serves as the instrument inlet is connected through a port 53 @wenn the bore-@Eis infturnoonnected o-theidiseharge A Y IineliZfbymeans-ofan'outletf.4 l

fs'iidabiy-mountedwithin fa' bushing 'SDin "the bore i 5 in sucht-manner" asto' 1`e``n'e Iichaliibersl 45a and-'45h' at \'thefoppositefends-'thereof is -`skiitd l"piston-51. In thelskirtedportion-fofthe is a series'olprts 58`i`n -a groove e"Staf adaptedfor alignmentwith-bushing ports Bfl'fegisterin with the annularfgroove v54, in order that {a`.2`i'1ovofy oil may take place from bore 44 ito lc`h`ar'1iber '45a in back ofpiston 51er at-"the'left therolaslvivd in'EFig;v` 3, Motion 'of' the^-pistonl51 giitwar o r 'forward under thepressre ofthe La"'sirxiit'ted Vthrugh ports f 58 "is -f resisted by -l'a spring '59 "iin chamber 45h, compressed-between the'fffronten'd of* the 'piston and an apertured ldisc 6| hel'd against movementby a spring clip 6 2." In Athe 'absence of any1overbalancingipressre vthespi'iig `59:'-h'o1ds the pistoni 51 seated'againstfthepIate "41 ,i-'Witn the ports 53 fully -open vto-the"'flow of'f'oil froin'the grooveV 54,- The piston 51is-formedwith Vallong'itud'inal opening in Whichfis fixed atube `63 dening a restricted elongated passage 64 by vlfiiclf'i oil m'a'yffiow from the'chamber'liafi the rear l of pistoni 51-lto the 'ch'amb'er y4517 in 'advance thereof. Itfmay berecogniied thatfthev tube 63 is constructed and ar'rangedasV aYYY friction tube that it offers frictional resistance tothe passage vof' oilv therethrough. It iis 'ajharacteristicfoff the `vfriction tube that the rate of flow' therethrough varies inversely With'- changes in' thevis'cosity vfof 'the oil. Thus'anincreasedwscosity ofutheoil admitted to inlet {boreMl` andnchambe ducesithe ratel of flow throughftube 6 A lowered viscosity increases"the` irate Yof flow'.

raiectfthe pressure in chamber dbjtvhich'pressure 'is determnied by the degree foffrestriction imposed on the escapefof'the oilthrough'opening 55 -to bore '46 andthe outlet.v Positioned Vwithin the-opening- 551sl a ported 'bush'ingt Y Mr conne'ct'edto -asimilarlyloffset-portion of arod containing a flow `restricting "dis'c 66V (seeFigff8) vformed with anoriiice-(H,y Since the` quantita- 'tive fiow through orice-61visr`xed'in accordance with the quantitative oW Ythrough 'tube 63 ,'1- the pressure requiredto force the'oil'from chamber l l n wesp ng typekno'wn commerciallyfas a micro 45D through the ori'ice'4 isgreater; under-antiin- "cre'ased 'flow vinto the chamberl than under4v a'-'reduced flow. Therefore,r momentarily lassin'l'ing 'theoriice 51 to have a VfixedY area, the pressurenin chamber 4527' willV rise-and jfalla'si thefrate 'of fiw `through the tube 63 is increased-and decreased.

' The opposed iiuidpressure'sat thefoppo'site ends Aof* the piston `51 are "heldf to ajpredetern'iined rei lation by movement "of the p'istonn 'relativeto the vfa'gn'rmlar groove 54 to admitA Ymore or" less oil to 420 iii-as 'chfehmbn thepr'essure in'eithertchaniber may-'libe used` as`r aameasurement fsviscosity and bfeanseditofinitiate s'oineoperation. Ithe system 'when ah1 predetermined 10W flor -Lh-igh- -viscosityhis -freac'hed 'Whicheverflpressureislselectedvmayvbe 'dsribedias f thecontroi pressure ofiv the yinstru:- l'nient, f-`1In the f'illustrative embodimentfiof..the-:invention the pressure in chamber 45a is usedl'as thei operation initiating fforce, being transmitted 'fhanber i451). Pi'sto'nBB Itherefore is subjectif'at one ehdftothe 'samei-press'ure-existingin chamber f'ai and at' the voti'ier-e'nzzi f-to fwhatever `Vpressure f be pr'esenltf at ithefo'utlet 5S. The Youtlet #56 restrictedy communication fWith the crankicase 'aridi-therefore. is at whateverfpressurelmay v "eX-iistin thecrankcase. Sornelbaek pressureis always present lin/'the Y discharge line,` but-1` "since lthisfpr'es'sure is exerted simultaneousiyasa force 'opposition toi-.thel pressure in chamberdagits action is neutralized.' Theprimary force"oppos lingfrnovement Sof-pis'toniBSunderthe pressure of loilin-f-chamber 46d@ is' alspri'ngl l vcompressed in *30 l`'itticiclfiamber146172between the pistonianda disc i.35 Aiathematical calculationfis--suiicient to prevent movement of the piston untilV apressure is reached 'F11 f' chamber 46a-indicating`lthat the oil' has Latftain'ed IAa `desired conditionoff-viscosity. -Motion ffthe pistori69 is here-vemploye'dlto operate-the 140 sWitch'lSE.' Asbest seeninFig. 6, airod'14 has one l'en'd in 'engagement Withthepiston 69fand exitehds'lthrough a' guide openingin disc A12^aiid through thefc-hamber 1 46h toward the fclosure '49. The-foppositefendof A"the rodv is offset and pivotally sv/itch. -`It'will'b'e'evi'ient', however, thatl any conventional' switchY may "fbe used inA connection vvit1'i'the vviscosity respor'sive instrurnent, V'the switchfbeing normally-closed; *and opened' by "'ifastened -by f=screws` to fthe instrument body? 31. Theclosure V49 isin nthefformf'of a bushing "48a and has a metallic "iiez'iblefTdiaphragrn -11i`xed v/tolits' inner endl The' diaphragm T77T1 has )an the chamberhlaa. -YDufingopepation'ofthe 'en-gineioo jcpeninsfor the passage ofvle'ver itherethrough,

the piston 51m'a`y make adjustments forward fand rearward-to reduce-and increase: theratepfiibw frominietb'ore 44' and vthereby `vary'tlfie pressure 'in chamber `4450i vin correspondence'withpre sure fthelever-fand' diaphragm being madeinte'gal Y'by afsolde'ringorflike process at lthe' point of said opening, The connection eiected by thelever '1151ar1'd'idiaphragm '11 is suchthattheiever is stent by the niet control adjustmentsrgfiiston *17o anges "fat hefi'struthereof. vdownward as the temperature of the oil is respring to return the lever` 15 to nrmal when the actuating pressure of the piston 59 is ref leased. In order that the diaphragm 11 and lever 15 will not tend to move outward, under the force of pressure in chamber 5517, a limit pin 80 may be passed transversely through the lever and arranged to abut the inner end of bushing It will be observed that the instrument asthus far described does not distinguish in its operation between changes of oil viscosity resulting from changes in the temperature of the oil and changes in viscosity brought about by dilution. That is, when the oil becomes suficientiy low in viscosity to enable the pressure in chamber 45a to overcome spring 1i operation of the piston will be initiated whether such degree of viscosity was attained by natural or artificial means. Although the instrument may function advantageously in a system where it is desired accurately to measure changes in viscosity resulting from temperature fluctuation it is here its purpose to measure only the viscosity change induced by dilution. Therefore temperature is eliminated as a factor in creating a predetermined pressure rise in the chamber 45h, and corresponding pressure increases in the chambers 65a and lita.. This is accomplished by varying the size of the orice B1 in direct accompaniment with variations in the temperature ofthe oil. As a consequence of such action any increase in flow through the friction tube 63 which is the function of lowered viscosity resulting from a temperature rise, is compensated for by an increase inthe area of oriice 61, allowing a less restricted flow of fluid to vthe outlet and preventing a rise in pressure in chamber 45h. Referring to Figs. 3 and 8, the mechanism for effecting such variations in the size of the orifice includes a taper or needle valve 19 formed integral with or otherwise secured to a piston 8l movable in the bushing 65 and triangularly or otherwise shaped to permit the passage of oil therearound. The needle valve 19 passes centrally through the orifice 5.1 and, in accordance with conventional constructions of this kind, is reciprocable to increase and reduce the width of the annular area between the peripheral surfaces of the valve and orifice. A spring 82 confined in the bushing 65 presses the valve 19 toward a position of maximum restriction of the orifice while movement of the valve in the opposite direction or to a position of minimum restriction is accomplished by a thermal element 83 which is stationed within the chamber 45h and in engagement with the valve. ment 83 is exposed to the oil entering chamber 4Gb, and as the temperature of the oil rises, the element reacts on a stationary pilot pin `8l! and moves upward, forcing the needle valve 19 backward out of the orifice to increase the open area A spring 85 returns the element 83 duced.

In the operation of the system, the manually operated switch 35 normally stands open and the solenoid valve 2'! is closed so that the lubricating oil tends to assume its natural state. Also, the switch 35 is closed and the elements of the instrument 31 are positioned as shown in Figs. 3 and 4, with the pistons 51 and 59 in their extreme left hand positions and the needle valve 19 moved adistance toward maximum restricting position determinedby the coldness of the oil. When the engine is started the pumps 22 and 24 begin circulation of theoil, directing it to and AALU iromthe engine, andalso to the instrument 31 by' way of linelll, through the instrument, and then tothe cilankcase by way of line 42.v The oil enters bore 4d in instrument 31 through gland 5i and screen 52 (Fig. (i) and isallowed to flow from the inlet bore to bore 45 through port 53, groove 54 and the series of ports 58 in piston51. Inside the b ore 45 theoil is permitted access by means of groove 68 to the rear of piston B9 and to friction tube 53, and passes through the latter to the front of piston 51 or chamber 45h. Passing through the orifice 61 to bore 4 6 and the outlet 56 the oil circulates freely and the control pressureestablished in chamber 43a is lbelow that necessary to move the piston 39 against the force .of spring 1 I. As operation of the engine warms theoil, the vi-scosity thereof becomes lower and the rate of flow through friction tuber53 increases in a manner tending to raise the pressure at the opposite ends of the tube because of the additional resistance of the orifice to the increased flow. I-lowever, as the higher temperature lowers the oil viscosity it -simultaneously causes anoperation of the thermal element 83 which moves the valve 1Q a distance to increase the open area oforice 61, thereby allowing the oil in chamber 45h to escape more easily. Under the control of the thermal element 83 and spring 82, compensating adjustment of the valve 19 continues throughout operation of the engine as the oil viscosity and temperature change in response to different night conditions and engine speeds, No opportunity is afforded for the oil pressure to rise sufficiently to overcome spring 1I, and the piston 69 accordingly remains inactive.

When it is desired to bring about oil dilution, with the engine running the operator adjusts the switch 35 to close the solenoid operating circuit, either through the all manual line 38 or through the-'automatic line 33, The valve 21 opens in response to such adjustment and, if the circuit is established through line 38, the gasoline flows from line 25 into the oil fitting I3 until the operator estimates that dilution to the'desired extent `has been obtained, whereupon he opens switch 35 cating Ythat dilution has ceased. Moreover, that act can vbe omitted should it Abe desired to permit the instrument 31 to maintain a constant degree of dilution.. Them the switch 35 would be left closed through theV automatic line 33 to cause dilution to be both started and discontinued under the control of switch 36.

lWhen, in response to the opening of the valve 21 dilution of the oil begins, a gradual lowering of the viscosity of the oil takes place, which process is not the result of a temperature change. Consequently, the instrument 31 responds to the increased rate of flow that takes place through .friction tube 63, in that the pressure in chamber Vthrough rod 14 to the lever 15, rocking the lever to separate the contacts of switch 36 and break the solenoid operating circuit. As previously indicated the relation between kthe pressure of spring 'H and viscosity may be predetermined to the end that operation of the pi-ston 69 will take place when the oil reaches a certain percentage of dilution, for example, 70% oil and 30% gasoline in the immediate lubricating line. By adjustment of the spring il or the substitution therefor of one having a greater or lesser strength the amount of dilution obtained may be varied.

It will be understood that the invention has been disclosed in merely one of the forms it may assume and that modification may be made in the use, mode of operation and structural details of the system without departing from the spirit or scope of the invention.

What is claimed is:

1. In an engine lubrication system, an engine, an oil storage tank, means for iiowing oil from said tank to 'and through said engine and back to said tank, a source of diluent, a conduit for conducting diluent from said source to the 'llowing oil, means for controlling flow through said conduit including an electromagnetically operated valve, said valve being normally closed, an electrical circuit including said electromagnetically operated valve and adapted when closed to effect movement of said valve to open position, first and second switches arranged in series in said circuit, said rst switch being normally open and said Vsecond switch being normally closed, means for closing said iirst switch, and means having its operation automatically initiated by the attainment of a predetermined percentage dilution in said lubricating oil for opening said second switch.

2. In an engine lubrication system, an engine, an oil storage tank, means for flowing oil from said tank to and through said engine and back to said tank, a source of diluent, a conduit for conducting diluent from said source to the flowing oil, means for controlling ow through said conduit including an electromagnetically operated valve, said valve being normally closed, an electrical circuit including said electromagnetically operated valve and adapted when closed to effect movement of said valve to open position, parallel leads forming a portion of said circuit, a rst switch normally closed in one of said parallel leads, means having its operation automatically initiated by the attainment of a predetermined percentage dilution in said lubricating oil for opening said first switch, and `a second switch in series with said first switch, said second switch being normally lopen and settable to close the .circuit alternatively through said parallel leads whereby to render said automatic means alternatively effective and ineffective to interrupt said circuit.

3. In an engine lubrication system, an engine, an oil storage tank, means for owing oil from said tank to and through said engine and back to said tank, a source of diluent, a conduit for conducting diluent from said source to the owing oil, means for controlling flowthrough said conduit including a valve settable to open and closed positions to begin and to discontinue the dilution process, said valve being normally closed, means for opening said valve and for applying a holding force maintaining said valve open, means for measuring the reduction in viscosity of the lubricating oil caused by dilution, and means having its operation automatically initiated by said measuring means in response to the attainment of a predetermined percentage dilution in said lubricating oil for interrupting the application lof holding force to said valve to permit closing of said valve.

4. In an engine lubrication system, an engine, an oil storage tank, means for owing oil from said tank to and through said engine and back to said tank, a source of diluent, a conduit for conducting diluent from said source to the flowing oil, means for controlling flow through said conduit including a valve settable to open and closed positions to begin and to discontinue the dilution process, said valve being normally closed, means for opening said valve and for applying Aa holding force to maintain said valve open,

means responsive to a decrease in viscosity of the lubricating oil caused by dilution to interrupt the application of holding florce to said valve to per-mit closing of said valve, and means preventing the operation of said interrupting means until a predetermined percentage dilution value of the oil is attained.

5. Inan engine lubrication system, an engine, an oil storage tank, means for iiowing oil from said tank to and through said engine and back to said tank, a source of diluent, Ia conduit for conducting diluent from said source to the flowing oil, means for controlling ow through said conduit including a valve settable to open and closed positions to begin and to discontinue the dilution process, means biasing said valve to closed position, manual means for moving said valve to open position, means having motion in response to decreased oil viscosity caused by dilution for rendering said manual means ineffective whereby to permit closing of said valve, and means inhibiting motion of said last named means to close said valve until the percentage dilution of said lubricating oil attains a predetermined value.

6. In an engine lubrication system, an engine, an oil storage tank, means for owing oil from said tank to and through said engine and back to said tank, a source of diluent, a conduit for conducting diluent from said source to the ilowing oil, means for controlling flow through said conduit including a valve settable to open and closed positions to begin and to discontinue the dilution process, means biasing said valve to closed position, actuating means for said valve including means operable to open said valve to begin dilution, a device for measuring the percentage dilution of the oil, and means operable automatically by said device upon attainment of a predetermined percentage dilution value to render said valve opening means ineffective whereby to permit closure of said valve to discontinue dilution.

HARRY T. BOOTH. ALLAN C. HOFFMAN. JAMES D. OLCOTT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,944,243 Kegl Jan. 23, 1934 2,121,045 Paynter June 21, 1938 2,146,930 Bassett Feb. 14, 1939 2,176,471 Pyle Oct, 17, 1939 2,208,444 Bailey July 16, 1940 2,311,069 Miller Feb. 16, 1943 

